Code amount control is a technique to optimize an image quality by controlling a generated amount of code (see, for example, Patent Literatures 1 and 2 below). In existing code amount control algorithms, code amount control is generally performed GOP (Group Of Picture) by GOP or frame by frame. In code amount control of frame by frame, for example, an amount of code allotted for one frame is calculated, and a quantization parameter for each macroblock within the frame is controlled so as not to exceed the amount of code.